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Difference between polarity and phase w/sub

In my Anthem AVM20 setup menu there are adjustments for polarity (normal and inverted) and phase (0-180) for the subwoofer output. When I change one or the other it seems to make the same difference. Can anybody give me an explanation of the difference between the two? I have an idea but just want to be sure.

Thanks,
prpixel
prpixel OP
876 posts
 
Thanks for the replies. Thanks Herman for the indebt definition of phase. I knew that inverting polarity means to switch the positive and negative lead, but was not sure about phase.

Herman:

If my sub is located between the main speakers but is about 3 feet behind them, how should I set phase?

Thanks,
prpixel
herman
2,216 posts
 
You adjust the knob until it is in phase with the mains. You will know this because the bass will be strongest at this setting. It can be done by ear but is much easier with a test recording and a sound pressure level meter. Play frequencies near the sub/main crossover frequency and adjust phase for maximum volume.
akgwhiz
177 posts
 

I had the same questions about phase control on a sub.  Most have them.  With the vast majority this is best put as phase "at 80 hz".  It's implementation is a simple time delay, milliseconds.  For example, 180 degrees reversal is really an "equivalent" done with  time delay such that 80hz is fully out of of phase with the main since the half wavelength in time of 80hz can be defined by time.  Around 32ms.  Set to 90deg and it's really a 16ms delay.  Effectively 90deg at 80 hz but now fully out at 160hz.  The good news is that subs have low pass cutoffs and often slopes to play with.  Personally I'd start at 90deg so that mains to sub handoff isn't boosted with a bloom nor suck-out at most affected/audible overlap area or... 80hz.   Vary from there to match room/sitting position.  The knob exists to control bloom/suck-out.  Setting to "most bass'" may just be bloom or room node.

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